Narrow safety range of intraoperative rectal irradiation exposure volume for avoiding bleeding after seed implant brachytherapy

Radiation Oncology

Tomoaki Fujioka⁴  Hisanori Ariga¹  Satoshi Yamaguchi³  Ikuko Uwano²  Tomonori Yabuuchi¹  Susumu Tanji⁴  Koyo Kikuchi¹  Ryuji Nakamura³ 

[1] Department of Radiology, Iwate Medical University School of Medicine, Uchimaru 19-1, Morioka, 020-8505, Japan;Iwate Medical University Advanced Medical Research, Uchimaru 19-1, Morioka, 020-8505, Japan;Iwate Medical University PET-Liniac Advanced Medical Center, Uchimaru 19-1, Morioka, 020-8505, Japan;Department of Urology, Iwate Medical University School of Medicine, Uchimaru 19-1, Morioka, 020-8505, Japan

关键词: dose-volume histogram;    brachytherapy;    prostate cancer;   

Others  :  1160901
DOI  :  10.1186/1748-717X-7-15

 received in 2011-06-25, accepted in 2012-01-31,  发布年份 2012

【 摘 要 】

Background & Purpose

Rectal toxicity is less common after ¹²⁵I seed implant brachytherapy for prostate cancer, and intraoperative rectal dose-volume constraints (the constraint) is still undetermined in pioneering studies. As our constraint failed to prevent grade 2 or 3 rectal bleeding (bled-pts) in 5.1% of patients, we retrospectively explored another constraint for the prevention of rectal bleeding.

Materials and methods

The study population consisted of 197 patients treated with the brachytherapy as monotherapy using real-time intraoperative transrectal ultrasound (US)-guided treatment at a prescribed dose of 145 Gy. Post-implant dosimetry was performed on Day 1 and Day 30 after implantation using computed tomography (CT) imaging. Rectal bleeding toxicity was classified by CTC-AE ver. 3.0 during a mean 29-month (range, 12-48 months) period after implantation. The differences in rV100s were compared among intraoperative, Day 1 and Day 30 dosimetry, and between that of patients with grade 2 or 3 rectal bleeding (the bled-pts) and of the others (the spared-pts). All patients were divided into groups based on provisional rV100s that were increased stepwise in 0.1-cc increments from 0 to 1.0 cc. The difference in the ratios of the bled-pts to the spared-pts was tested by chi-square tests, and their odds ratios were calculated (bled-OR). All statistical analyses were performed by t-tests.

Results

The mean values of rV100us, rV100CT_1, and rV100CT_30 were 0.31 ± 0.43, 0.22 ± 0.36, and 0.59 ± 0.68 cc, respectively. These values temporarily decreased (p = 0.020) on Day 1 and increased (p = 0.000) on Day 30. There was no significant difference in rV100s between the bled-pts and spared-pts at any time of dosimetry. The maximum bled-OR was identified among patients with an rV100us value above 0.1 cc (p = 0.025; OR = 7.8; 95% CI, 1.4-145.8); an rV100CT_1 value above 0.3 cc (p = 0.014; OR = 16.2; 95% CI, 3.9-110.7), and an rV100CT_30 value above 0.5 cc (p = 0.019; OR = 6.3; 95% CI, 1.5-42.3).

Conclusion

By retrospective analysis exploring rV100 as intraoperative rectal dose-volume thresholds in ¹²⁵I seed implant brachytherapy for prostate cancer, it is proved that rV100 should be less than 0.1 cc for preventing rectal bleeding.

【 授权许可】

   
2012 Nakamura et al; licensee BioMed Central Ltd.

【 图 表 】

Figure 1.

Figure 2.

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